The motorist, moving at a speed of 30 km / h, drove half the way to the destination in a certain period of time.
| March 2, 2021 | education
The motorist, moving at a speed of 30 km / h, drove half the way to the destination in a certain period of time. At what speed should he continue to move in order to reach the goal and return back in the same time?
V1 = 30 km / h.
S1 = S / 4.
S2 = 3 * S / 4.
t1 = t2.
V2 -?
The entire distance traveled by the car is S. The distance to the destination is S / 2. Since the motorist drove half the distance to the destination, then S1 = S / 4 he traveled all the way at a speed of V1. So the path S2 = S – S1 = 3 * S / 4 he was traveling at a speed of V2.
t1 = S1 / V1 = S / 4 * V1.
t2 = S2 / V2 = 3 * S / 4 * V2.
S / 4 * V1 = 3 * S / 4 * V2.
V2 = 3 * V1.
V2 = 3 * 30 km / h = 90 km / h.
Answer: the driver must drive at V2 = 90 km / h.
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